Everting stent and stent delivery system

ABSTRACT

A delivery device includes a delivery tube having an elongate release member. An everted stent may be releasably captured by the elongate release member between the release member and the delivery tube. The captured and everted stent can be distally advanced to a target site, followed by manipulating the release member to free the captured stent. Some devices utilize distal advancement of the release member while other devices use proximal retraction of the release member to free the captured stent. Once released, the stent is free to self-expand or be expanded against the surrounding blockage and/or vessel walls. In some methods, a guide catheter or microcatheter is also included and disposed about the everted and captured stent to advance the stent, delivery tube, and release member to a location near the site to be stented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/035,671,filed Jan. 14, 2005, now abandoned which is a continuation ofapplication Ser. No. 10/096,628, filed Mar. 12, 2002, now U.S. Pat. No.6,866,679, the entire contents thereof are incorporated herein byreference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to medical devices. Morespecifically, the present invention relates to stents. The stents mayfind particular use in intravascular procedures in general, and incardiovascular procedures in particular, as well as other areas.

BACKGROUND OF THE INVENTION

Stents are well known to those skilled in the biomedical arts. Inparticular, stents are commonly used in cardiovascular applications.Stents have gained increasing acceptance, particularly when used inconjunction with minimally invasive procedures such as angioplasty.

Blockages of the coronary arteries may result from various causes,including plaque build-up, and stenosed or thrombosed vessel regions.The vessel regions thus partially occluded can cause angina and, whentotally occluded, myocardial infarction, and even death. Minimallyinvasive procedures such as balloon angioplasty have been used to dilatesuch blocked vessel regions, thereby at least partially restoring patentvessel lumens.

In a significant percentage of cases, a stenosed, then dilated vesselregion may narrow after treatment over a period ranging from days tomonths. This re-narrowing or restenosis, limits the efficacy of theangioplasty procedures, may require further angioplasty, or can lead tomyocardial infarction and even death.

Cerebral blockages are typically caused by a thrombus. The thrombus canform or lodge in a cerebral artery, preventing brain regions downstreamfrom receiving perfusing blood flow. The loss of oxygen can rapidlycause brain death in the affected brain regions if the blockage is notsoon treated. The cerebral arteries are generally smaller and moretortuous than the corresponding coronary arteries. The required timingand difficult vessel characteristics make reaching and treating thethrombus to prevent brain cell death a most difficult task. The narrowcerebral vessels make placing stents within the brain very difficultusing current stents and stent delivery systems. Microcatheters arecurrently used to infuse drugs into cerebral blood vessels. Themicrocatheters are typically not greater than about 4 Fr. (1⅓ mm.) inouter diameter, currently being generally unsuitable for delivery ofcerebral stents.

Stents have been extensively utilized in an attempt to prevent or limitrestenosis. Stents are typically tubular devices delivered to thestenosed and dilated site. The stents can be expanded into place againstthe treated region walls, hopefully preventing restenosis and furthernarrowing at the stented location. Stents are often formed of metal,commonly stainless steel or Nitinol. The stents can be open walledstructures formed from lattice-like cages, spiral wire structures,braided structures, and helically wound and counter-wound structures.Stents can be self-expanding, designed to expand radially when distallyadvanced from a restraining delivery catheter. Stents can also beballoon-expandable. Balloon-expandable stents can be positioned and thenexpanded from within using a stent delivery balloon and/or anangioplasty balloon.

A typical stent delivery device includes a stent constrained within anouter delivery sheath extending over the length of the stent. When thedevice is advanced to the target site, the outer sheath is proximallyretracted and/or the stent is distally advanced from within the sheathto the target site. The delivery sheaths may work as intended, but doadd bulk to the distal end of the delivery device. In particular, thedelivery sheath adds at least one additional layer surrounding thestent. The delivery sheaths are generally cylindrical in nature andextend over the entire length of the stent. The stent can act toreinforce the outer sheath. The delivery sheath and enclosed stent thusact to form a rather rigid composite structure that is not as able tobend and traverse the tortuous vessel regions often found in the humanbody. The composite structure is thus not as flexible as either thestent or sheath alone would be in traversing these passages.

The added bulk and profile or cross-sectional area of the deliverydevice can thus act to restrict the use of such stents to largervessels. In particular, this may leave smaller vessels unreachable anduntreatable. Sites requiring treatment disposed on the distal side of atortuous curve may also be unreachable and untreatable.

In use, some currently available stents and delivery systems also haveanother limitation. For self-expanding stents, stent placement is oftenimprecise. The placed or final stent length is related to the finalstent diameter that is related to the vessel diameter. Within a vessel,the diameter is not always precisely known, and can vary over the regionto be stented. It may be nearly impossible to predict the final stentlength before the stent is fully expanded in the vessel.

The difficulty in accurate stent placement can become an issue instenting a vessel ostium. It is often desirable to place a stentprecisely at the ostium of a vessel, especially in coronary and renalvessels. If the stent is positioned too proximal, the stent extends intothe trunk line, and can cause flow disturbance. If the stent ispositioned too distal, the disease at the ostium is not treated.Self-expanding stent delivery systems typically deploy the stent fromdistal to proximal, with the distal stent end being advanceddistal-most. In particular, a self-expanding stent may be advanced whiledisposed within a delivery sheath. When the sheath distal end is inposition, the sheath can be retracted, allowing the accurately placedstent distal end to expand first. The proximal end of the stent can varydepending on the vessel diameter. In order to accurately place the stentproximal end, the treating physician thus needs to guess at the positionto start stent deployment based on the assumed final stent length, sothat the proximal end of the stent ends up at the precise ostiallocation desired.

What would be desirable are devices and methods for delivering stents totarget vessel regions that do not require the added bulk of an externalrestraint or capture sleeve over the stent. Applicants believe thatdevices and methods not absolutely requiring a delivery sheath over thestent would allow smaller, more tortuous, and more distal vessels to beeffectively treated.

SUMMARY OF THE INVENTION

The present invention includes devices and methods for delivering stentsto target vessel regions within the body. Methods and devices fordelivering everted stents are preferred and disclosed. One stentdelivery assembly includes a delivery tube having a stent slidablydisposed over the delivery tube distal region, and having the stentdistal region everted over the delivery tube distal end, such that thestent distal end is tucked inside of the delivery tube distal end lumen.An elongate release member having a distal element can be slidablydisposed within the delivery tube lumen. The release member distalelement can be dimensioned relative to the surrounding delivery tubedistal end inside diameter so as to form a tight fit between the releasemember distal element and the surrounding delivery tube. The stentdistal region can be held by a friction or interference fit between therelease member distal element and surrounding delivery tube walls. Thestent is thus everted and reduced in outer diameter at the leading,everted distal end.

In one delivery device, the elongate release member is pulled from theproximal region, thereby proximally urging the release member distalelement free of the stent distal end captured between the release memberdistal element and the surrounding delivery tube distal end. In suchembodiments, the release member function may be served by an elongatestring or wire having significant strength mainly in tension rather thancompression. In another embodiment of the invention, the elongaterelease member function is served by a shaft having sufficient strengthin compression to distally urge the release member distal element bymanipulating the release element proximal region, forcing the distalelement from the surrounding delivery tube distal end, thereby freeingand unconstraining the stent distal region. In some embodiments, thedelivery tube functionality is served by a delivery shaft having onlythe distal region being tubular in nature. In one such embodiment, thedelivery shaft has a distal hoop or annular ring for surrounding andcapturing the everted stent distal region within.

In use, the stent can be everted over the delivery tube or shaft, withthe stent distal end everted and captured by the elongate releasemember. The everted stent, delivery shaft or tube, and release membercan be advanced distally to a target vessel region to be stented. Onceat the target region location, the everted and constrained stent may befreed of the delivery shaft or tube by the release member. The releasemember may be retracted proximally in some embodiments, and advanceddistally in other embodiments, as previously discussed, to release theeverted stent. Once released, the stent is free to expand radially andapproach the surrounding vessel walls or blockage.

Self-expanding stents can be used in some embodiments of the invention.The stents are preferably biased to radially expand when freed of theconstraints of the delivery tube and release member. In otherembodiments, balloon expandable stents are used, which can be expandedusing inflatable balloon catheters or other stent delivery devices.

Some methods according to the present invention can utilize a guide wireto facilitate advancement of a guide catheter or microcatheter to alocation near the vessel region to be stented. The guide wire can beretracted, and the carried everted stent advanced by the release memberand guide tube together through the guide catheter or microcatheter tothe target region. In one method, the everted stent carried by thedelivery tube and release member are advanced distally from the guidecatheter to cross the target region, for example, a blood vesselstenosis. In another method, the microcatheter together with the evertedstent carried by the delivery tube and release member are advancedthrough the stenosis or other blockage, followed by proximallyretracting the microcatheter, leaving the everted stent to expandagainst the target region vessel or blockage walls. Once the evertedstent is in location, the release member can be activated by advancingor retracting the member to free the everted stent.

Once unconstrained, the stent, for example, a self-expanding stent, mayexpand to approach the vessel walls or the blockage. In someembodiments, the release member may be advanced distally through thepreviously placed stent lumen to guarantee a minimal lumen through thestent and/or to act as a guide member for other devices to be passedthrough the now stented region. In one method, the delivery tube isadvanced through the now stented region, which can act to further dilatethe stent. In another method, the guide catheter or microcatheter canalso be advanced through the now stented region, which can act tofurther dilate the stent. Thus, a succession of ever increasing diameterdevices may be advanced through the stent after stent deployment in somemethods. In another method, a balloon catheter is advanced through thenow stented region followed by inflation of the balloon and concomitantdilation of the stent.

In another use of the present invention, an everted porous stent carriedby a delivery tube can be distally advanced through a thrombosed bloodvessel region. A wire mesh or braided stent may be used. The evertedstent can be released from the delivery tube to expand against thethrombus. The delivered stent can thus act to stabilize the thrombus.After stenting, the thrombus can be treated by infusing thrombolyticagents near the thrombus, through the walls of the porous stent. Thestent can thus act to stabilize the thrombus, preventing large piecesfrom breaking off and being carried downstream during the thrombolysis.

Some embodiments of the present invention have distally tapered deliverytubes having very small distal end profiles. In these embodiments, therelease member distal element may be very small in profile as well. Thelimit of the distal profile in such devices may approach the lower sizelimit in gathering, everting, and compressing the distal region of thestent to be delivered. In these and other embodiments, the leading edgeof the stent delivery device can be very benign and atraumatic due tothe everted stent forming the distal-most leading edge of the device.Many embodiments of the device thus eliminate the absolute need for adelivery sheath or tube disposed about the stent, thereby eliminatingone set of tube profiles from the device, making the distal region moreflexible, smaller in profile, and able to reach even more distal andsmaller diameter vessels which will benefit from treatment.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, longitudinal, cross-sectional view of a stentdelivery assembly including a stent captured between the distal ends ofan elongate release member and the surrounding stent delivery tube shownprior to everting the stent proximally over the delivery tube;

FIG. 2 is a fragmentary, longitudinal, cross-sectional view of the stentdelivery assembly of FIG. 1 after the stent has been everted and thedevice disposed within a guide catheter or microcatheter;

FIG. 3 is a fragmentary, longitudinal, cross-sectional view of the stentdelivery assembly of FIG. 2 after the microcatheter has been advancedproximal of a blockage and the captured, everted stent carried furtherdistally by the release member and delivery tube;

FIG. 4 is a fragmentary, longitudinal, cross-sectional view of theassembly of FIG. 3 after the stent has been released and expanded withinthe target vessel region;

FIG. 5A is a fragmentary, longitudinal, cross-sectional view of analternate embodiment of the invention where the delivery tube is adelivery shaft having a distal tube or ring;

FIG. 5B is a wafer view taken through 5B of FIG. 5A, illustrating thefit between the release member distal end, everted stent, and deliveryshaft distal end; and

FIG. 5C is a fragmentary, longitudinal, cross-sectional view of anotherembodiment of the invention, where the delivery tube has a tubulardistal region and coupled to a proximal shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are numberedidentically. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theinvention. Several forms of invention have been shown and described, andother forms will now be apparent to those skilled in art. It will beunderstood that embodiments shown in drawings and described above aremerely for illustrative purposes, and are not intended to limit scope ofthe invention as defined in the claims that follow.

FIG. 1 illustrates a stent delivery assembly including a stent deliverydevice 20, a stent 26, a delivery shaft or tube 22, and an elongaterelease member 24. Release member 24 can be used to releasably secure orcouple stent 26 to delivery shaft or tube 22. Stent 26 is illustrated ina configuration prior to being everted and proximally disposed aboutdelivery tube 22. Delivery tube 22 may be seen to have a distal region30, a distal end 28, an intermediate region 32, a tube wall 38, a tubewall inner surface 36, and a lumen 34 therethrough. Release member 24may be seen to have a distal region 40 and a distal end 42 having adistal element 43. In the embodiment illustrated in FIG. 1, releasemember distal end 42 is dimensioned so as to form an interference fitbetween stent 26 and delivery tube wall inner surface 36. Delivery tubewall 38 may be seen to be slightly distended in the area of releasemember distal end 42. Stent 26, described with reference to the evertedstate, has generally a distal region 46, a distal end 47, anintermediate region 44, a proximal region 48, a proximal end 50, and alumen 52 therethrough.

Release member 24 may be seen, at distal end 42, to have an outsidediameter D1 which closely approximates the inside diameter of deliverytube 22 in the distal region. Stent 26 may be seen gripped betweenrelease member distal end 42 and delivery tube 22. Stent 26, in someembodiments, may be biased to expand radially when unconstrained. Asillustrated in FIG. 1, stent proximal end 50 has an unconstraineddiameter D2 that is substantially larger than the constrained diameterD1. Self-expanding stents are well known to those skilled in the art.Such self-expanding stents may be formed, for example, from Nitinol,which can be heat set to assume a desired shape when unconstrained.Stent 26 in FIG. 1 is illustrated in an intermediate step duringassembly. Stent proximal end 50 may be everted and pulled proximally asa sleeve over delivery tube 22. Other methods of assembly are possible.In preferable methods, stent 26 may be heat set in an uneverted shapeand disposed as a sleeve over delivery tube distal region 30 in theuneverted state. Stent distal region 46 may then be everted and tuckedwithin delivery tube distal end 28. Release member 24 may then have itsproximal end threaded through stent lumen 52 and delivery tube lumen 34until release member distal end 42 has been proximally retracted withindelivery tube distal region 28, firmly capturing stent distal region 46between the elongate member distal end 42 and the delivery tube distalregion 28.

FIG. 2 illustrates stent delivery device 20 further included within amore comprehensive stent delivery assembly 60. Stent delivery assembly60 includes generally a guide catheter or microcatheter 62 having adistal region 64, an intermediate region 69, a proximal region 72, and adistal end 66 having a lumen 68 therethrough. Release member 24 can havean optional collar 51 disposed about the release member distal regionand dimensioned to slidably fit within delivery tube 22. FIG. 2 furtherillustrates release member 24 having a proximal region 25 coupled to anoptional larger diameter proximal end 27 dimensioned so as to form anaxially slidable seal between release member proximal end 27 and thesurrounding delivery tube proximal region 33. FIG. 2 also illustratesoptional annular seal member 29 forming a larger diameter proximalregion 33 for the delivery tube 22. Annular element 29 may be seen toform a slidable seal between delivery tube 22 and the surrounding guidecatheter or microcatheter 62. FIG. 2 also illustrates that stent 26 canexpand outward radially while within guide catheter 62. In particular,stent intermediate region 44, proximal region 48, and proximal end 50may be seen to have expanded radially to the extent permitted by thesurrounding guide catheter 62. The dimensions illustrated for theproximal region of stent delivery assembly 62 and FIG. 2 may varydepending on the embodiment and the intended use. FIG. 2 illustratesonly one, non-limiting example of the invention.

Microcatheters are well known devices, commonly used to deliver drugs tocerebral arteries. “Microcatheters”, as the term is used herein, isdefined to be a tubular catheter having an outside diameter less thanabout 5 Fr. (1⅔ mm.). Microcatheters used with the present inventionpreferably have an outside diameter between about 1.5 Fr. (½ mm.) and 4Fr. (1⅓ mm.), inclusive. Microcatheters preferably have a floppy distalregion and tip, the distal region being more pliable and softer than theintermediate and proximal microcatheter regions.

FIG. 3 illustrates one use of assembly 60 in a body conduit or vessel 82having a target region 80 at least partially occluded by a blockage 84.Blockage 84 can at least partially block vessel 82, thereby reducing theeffective size of vessel lumen 86. Blockage 84 represents any of anumber of blockages, including, but not limited to plaque, thrombus, anda stenosed vessel region generally.

In one method according to the present invention, a guidewire isadvanced distally through the vessel until the guidewire distal tip isacross or proximally near vessel target region 80. Guide catheter ormicrocatheter 62 can then be advanced over the placed guidewire untilmicrocatheter distal end 66 is disposed proximal of blockage 84. In somemethods, the guidewire is now retracted proximally from microcatheter62.

With microcatheter 62 in place, stent delivery device 20 may be advancedthrough microcatheter lumen 68 to a position within microcatheter 60proximal of vessel target region 80. As may be seen from inspection ofFIG. 3, stent 26 is everted over the distal end of delivery tube 22 andreleasably secured to delivery tube 22 with elongate release memberdistal end 42. In the embodiment illustrated, stent 26 is aself-expanding stent, with proximal end 50 having a larger outsidediameter than constrained distal end 47.

With release member 24, delivery tube 22, and everted stent 26 inposition, the release member, the delivery tube, and the captured,constrained and everted stent 26 may be distally advanced across thetarget site 80 having blockage 84. In some methods, the advancing ofrelease member, delivery tube, and everted stent is accomplished whileleaving guide catheter or microcatheter 62 positioned proximal of thevessel target site. In other methods, guide catheter or microcatheter 62is advanced across target vessel region 80. In one method, microcatheter62, everted stent 26, delivery tube 22, and release member 24 are alladvanced together across target region 80. In this method, aftermicrocatheter 62 and constrained, everted stent 26 are across targetvessel region 80, microcatheter 62 can be proximally retracted, exposingthe stent.

As may be seen from inspection of FIG. 3, stent 26 is still releasablysecured to delivery tube 22 and may be further advanced distally. Insome uses of the invention, a microcatheter such as microcatheter 62 maybe used to advance the releasably secured stent and delivery tube onlyso far as the microcatheter can reach, followed by the distal exit ofthe everted stent from the microcatheter to attain even greater distalreach for the stent. FIG. 3 also illustrates that stent 26 can beaxially elongated as the stent is pulled through narrow passages, whichcan reduce the stent profile while the stent is being pulled.

Once everted stent 26 is at the desired location, the stent can bereleased from delivery tube 22. In one example of the invention, releasemember 24 is urged proximally, thereby pulling the release member distalend proximally until release member distal end 42 is disposed proximallyof everted stent distal end 47. Stent 26 may then expand furtherradially to embrace the surrounding vessel target region 80. In anotherexample of the invention, elongate release member 24 can be distallyurged, thereby forcing release member distal end 42 distally fromdelivery tube 22, thereby releasing stent 26 from delivery tube 22. Inembodiments having optional collar 51, the collar can be used to helppush out the stent after release. Both distal and proximal movement ofrelease member 24 can be accomplished by manipulating the proximallyaccessible portion of the release member. Stent 26 is then free toradially expand and retain its previous, non-everted shape.

It may be seen from inspection of FIG. 3 that everted stent 26 has asmaller distal profile than proximal profile, allowing easier entry intonarrow target sites. In some embodiments of the invention, delivery tube22 has a tapered distal tip, such that the profile of the distal end ofdelivery tube 22 is smaller than the profile of delivery tube 22 in anintermediate or proximal location. FIG. 3 also illustrates that theeverted distal region 46 of stent 26 forms a rather atraumatic tip,relative to many other distal delivery devices and, in most embodiments,more benign than the delivery tube distal end 28. Due in part to theself-expanding nature of the stent illustrated in FIG. 3, distallyurging the half released, half secured stent forms a proximally wideningshape that can act to initially penetrate, then dilate a blocked vesselregion, prior to totally releasing the stent.

The distance between release member 24 and delivery tube 22 is indicatedat D3 in FIG. 3. In some embodiments, the proximal and intermediateregions of delivery tube 22 have a very tight fit between release member24 and delivery tube 22. A close tolerance between the release memberand the delivery tube can provide columnar support for advancing releasemember 24. Such close tolerance can also provide strength and stabilitywhen the elongate release member 24 is retracted proximally to releasestent 26, in embodiments calling for such retraction.

FIG. 4 illustrates vessel target region 80 after stent 26 has beenexpanded to create and stabilize an expanded or dilated flow channel 87through vessel 82. Stent proximal region 48 and distal region 46 may beseen to have expanded radially against blockage 84. Stent 26 ispreferably radially expanded outwardly against the vessel walls and/orblockage once released by release member 24. In one method, stent 26 isbiased to radially expand outwardly, once unconstrained. Someself-expanding stents useful with the present invention are formed ofNitinol. Stents may be heat-set to radially expand and assume theheat-set diameter once released in some methods.

In one method according to the invention, after stent 26 has beenallowed to expand radially, this process may be assisted using parts ofthe device previously described. In embodiments where the release rodhas sufficient strength in compression to be pushed, release member 24may be advanced distally through deployed stent 26 to ensure that aninitial clear flow passage exists through stent 26. Elongate releasemember 24 may be followed by distally advancing delivery tube 22 throughdeployed stent 26. In other methods, guide catheter or microcatheter 62may be advanced through deployed stent 26, to further widen the alreadystented passage. These methods may also be employed to assist witheversion of the distal end of the released but incompletely deployedstent. In some methods, the delivery tube and release member may beretracted proximally, and an inflatable balloon catheter advanced to thenow stented vessel site to further dilate the deployed stent byinflating the inflatable balloon disposed in the balloon catheter distalregion.

FIG. 3 illustrates only one embodiment of the invention, which is notnecessarily drawn to scale. In particular, in some embodiments, thedistal region of delivery tube 22 can be significantly smaller inprofile. In one embodiment, release member 24 has distal end 42 beingsubstantially smaller in profile than that illustrated in FIG. 3. In oneembodiment, distal end 42 is tapered distally or proximally tofacilitate the frictional fit between the stent and the deliverycatheter. The inside of the delivery catheter distal region and/oroutside of the release member distal end 42 can be coated with acompressible, tacky, flowable, or high friction material to augment thesecurity of reversible stent engagement. In one device, release memberdistal end 42 is only slightly larger in profile than the intermediateportion of release member 24. In one embodiment, release member 24 hasstrength substantially only in tension rather than compression, and actsas a string. This string or wire can be very small in profile, and canbe coupled to a very small release member distal element. In oneembodiment, elongate release member 24 is a fine gauge wire, metallic orpolymeric, coupled to a small distal plug. Delivery tube distal end 28may also be much smaller and significantly distally tapered relative tothat illustrated in FIG. 3. Delivery tube distal end 28 may also bereinforced against diametric enlargement by incorporation of a strongcircular loop or band within or outside of the wall of the delivery tubedistal end. Preferably the loop or band is metallic and more preferablyradiopaque so as to facilitate visualization under fluoroscopy.

Inspection of FIG. 3 indicates that the lower limit on the transversecross-sectional size or profile of the stent delivery assembly may belimited by the profile of the everted stent 26. In one embodiment of theinvention, elongate release member 24 is effectively a thin wire orstring terminating distally in a plug or ball shape only slightly largerin profile than the wire or string. Delivery tube 22 may besignificantly distally tapered such that the inside diameter of thedelivery tube distal end approaches the outer diameter of the releasemember distal end or plug 42. The stent may thus be everted and thestent distal region tightly bunched or gathered together between thesmall distal ball or plug and the surrounding, tapered, distal end ofthe delivery tube. While the release member and delivery tube occupyspace, it may be seen that the absolute lower limit of thecross-sectional profile in some embodiments may be ultimately bounded bythe lower size limit in releasably compressing the stent distal end.

FIG. 5A illustrates another embodiment of the invention. The stentdelivery assembly 100 illustrated in FIG. 5A can be similar to that ofassembly 20 as illustrated in FIGS. 1 and 2. Delivery assembly 100 maybe seen to have an everted stent 26 and an elongate release member 24 aspreviously discussed. Assembly 100 has a delivery shaft 122 rather thana delivery tube. Delivery shaft 122 has an intermediate region 132extending to a distal region 124. Distal region 124 includes supportstruts 128 extending distally and radially outward to support a shorttube section or annular ring 126. In some embodiments, annular tube orring 126 may be significantly longer than that illustrated in FIG. 5A,which is not necessarily to scale. The distal region of delivery shaft122 may thus form a delivery tube in the many respects previouslydiscussed. Stent 26 may be seen to be everted over distal annular ringor hoop 126 and held in place by a tight, interference fit betweenrelease member distal element 43 and annular ring 126. As may be seenfrom inspection of FIG. 5A, everted stent 26 may be released from theassembly 100 by proximally retracting release member 24 or distallyextending release member 24, depending on the embodiment and theproperties of the release member shaft forming release member 24. FIG.5B illustrates a transverse cross-sectional view of the assembly 100 ofFIG. 5A, showing release end element 43 disposed within one layer ofstent 26 which is in turn disposed within annular ring 126 which has asecond layer of stent 26 disposed to the outside.

The distal region of delivery shaft 122 may thus form a delivery tube inthe many respects previously discussed. Stent 26 may be seen to beeverted over distal annular ring or hoop 126 and held in place by atight, interference fit between release member distal element 42 andannular ring 126. As may be seen from inspection of FIG. 5A, evertedstent 26 may be released from the assembly 100 by proximally retractingrelease member 24 or distally extending release member 24, depending onthe embodiment and the properties of the release member shaft formingrelease member 24. FIG. 5B illustrates a transverse cross-sectional viewof the assembly 100 of FIG. 5A, showing release end element 43 disposedwithin one layer of stent 26 which is in turn disposed within annularring 126 which has a second layer of stent 26 disposed to the outside.

FIG. 5C illustrates another stent delivery assembly 160, somewhatsimilar to that of delivery assembly 100 of FIG. 5A and having the samereference numerals for similar elements. Assembly 160 includes elongaterelease member 24 and stent 26 as previously discussed. The deliverydevice includes a distal tube 166 coupled to a proximal elongate memberor shaft 162. Tube 166 includes a proximal end 174, a distal region 170,a distal end 172, and a lumen 168 extending through the tube. Proximalshaft 162 can be coupled to tube 160 at a shaft distal region 164.Proximal shaft 162 can extend distally along or within tube 166 in someembodiments. Tube 166 may be slit to accommodate proximal shaft 162.

Stents that may be used with the present invention includeself-expanding and balloon expandable stents, well known to those in thecardiovascular arts. Stents may be formed from many of the well knownstent materials, including Nitinol, stainless steel, and polymers. Thestents may be braided, knit, meshed, formed of non-woven wires,helically wound and helically counterwound. Stents according to thepresent invention are preferably porous, wire, braided stents, withvarious embodiments having an average pore or inter-wire opening size ofat least about 20 microns in one embodiment, and at least 50 microns inanother embodiment. In a preferred embodiment the stent ends are coatedwith flexible adherent material to prevent unraveling of, for example,braided stents. Alternatively, the stent strands can be welded orotherwise fastened to one another to prevent unraveling during eversion.

In one use of the invention, the everted stent may be used to stabilizea blockage such as a thrombus, while providing a perfusing path throughthe dilated thrombus. In another use, the stent may be positioned acrossa stenosed blood vessel region, and the region treated with a restenosisinhibiting agent. The restenosis inhibiting agent can be infused throughthe porous stent wall or reside on the stent itself and release into thevessel wall. FIGS. 3 and 4 may be used to visualize blockage 84 beingformed primarily of thrombus, with stent 26 being put in place toprimarily stabilize the thrombus and to provide oxygenating blood flowto downstream brain regions, preventing brain cell death. Small distalprofile catheters as previously discussed and as illustrated in FIG. 3may thus be used to advance an everted stent across a thrombus anddeploy the stent. The stent, which can be either self-expanding orexpandable from within using a stent placement device, can then expandagainst the vessel walls and/or blockage. In some methods, an infusioncatheter is advanced to within vessel site 80, and thrombolytic agentsinfused through the porous stent wall. Various therapeutic agents may beapplied in this way. A non-limiting list of such therapeutic agentsincludes thrombolytic agents, anticoagulants, anti-platelet agents, andtissue plasminogen activator. In a similar way, stents according to thepresent invention can be used to treat an area stenosed because ofarteriosclerosis.

The present invention can be used to accurately position the stentproximal end. The stent proximal end may be positioned accuratelyrelative to a vessel ostium. The stent can be positioned near theproximal end of a stenosis located near or at an ostium. The evertedstent can be advanced as previously discussed, until the proximal end ispositioned at the desired location. The stent proximal end can beallowed to radially expand against the vessel walls. In some methods,the stent can be advanced further distally until the expanded proximalend is at the desired position. The stent placement may be followedusing fluoroscopy. This desired position may be exactly at the ostiumbeginning, slightly within the ostium, or extending slightly from theostium. The stent distal region can be released and allowed to expand.In this way, the stent proximal end can be positioned accuratelyrelative to the ostium.

In one embodiment of the invention, the elongate release member has alength of between about 100 cm. and 200 cm. In one embodiment, the outerdiameter of the release member distal element is less than 2 mm. Invarious embodiments, the release member may be formed from stainlesssteel, Nitinol, polyimide, reinforced polymer, or PEEK and the like.

The delivery tube or shaft in some embodiments has a length of betweenabout 75 cm. and 175 cm. The delivery tube can have an outside diameterof between about 6 Fr. and 1 Fr. In various embodiments of theinvention, the distal region of the delivery tube may be distallytapered. In some embodiments, the cross-sectional outer diameter of thedelivery tube distal end is less than about 6 Fr. Delivery tubes can bemade from flexible polymers such as PEBAX, nylon, polyester,polyurethane, polyethylene, FEP, Teflon, silicone, and the like, with orwithout reinforcement by metallic or polymeric elements. Microcathetersare well known to those skilled in the art and any suitably sized guidecatheter or microcatheter may be used in combination with the presentinvention, preferably about 3 Fr. or 4 Fr. in outer diameter. Someexemplary sized catheters that can be used with the present inventionare between about 75 cm. and 175 cm. in length. Guide or microcathetersuseful in conjunction with the present invention may be formed fromNylon, PEBAX, polyurethane, and the like. Guide catheters can bereinforced with metallic braids, with microcatheters preferably havingvery flexible distal end regions. The catheters can have a distal outerdiameter of less than about 8 Fr. for guides and 4 Fr. formicrocatheters.

1. A delivery device for delivering a stent, the device comprising: adelivery shaft defining a lumen; and an elongate release member disposedwithin the lumen defined by the delivery shaft, the elongate releasemember releasably securing an everted distal region of the stent betweena distal region of the elongate release member and a distal region ofthe delivery shaft when a distal end of the elongate release member isdisposed within a distal region of the lumen defined by the deliveryshaft such that a distal end of the everted distal region of the stentis disposed distally of a proximal end of the stent to releasably securethe everted distal region of the stent within the lumen defined by thedelivery shaft, wherein longitudinal movement of the elongate releasemember disengages the everted distal region of the stent from theelongate release member and frees the stent from the delivery shaft,wherein when the distal end of the elongate release member is disposedwithin the distal region of the lumen defined by the delivery shaft, thedistal end of the everted distal region is disposed within the lumendefined by the delivery shaft and the proximal end of the stent isdisposed outside of the lumen defined by the delivery shaft.
 2. Thedelivery device of claim 1, further comprising a microcatheter defininga lumen and including an inner surface and an outer surface, thedelivery shaft being supported within the lumen of the microcatheter,wherein a proximal region of the stent is disposed within the lumen ofthe microcatheter between the inner surface of the microcatheter and anouter surface of the delivery shaft when the distal end of the elongaterelease member is disposed within the lumen of the delivery shaft. 3.The delivery device of claim 2, wherein the delivery shaft includes aninner surface, the proximal region of the stent being supported betweenthe inner surface of the microcatheter and the outer surface of thedelivery shaft when the distal end of the elongate release member isdisposed proximally of a distal end of the delivery shaft to support theeverted distal region of the stent within the lumen defined by thedelivery shaft.
 4. The delivery device of claim 1, wherein the elongaterelease member distal region releasably secures the everted distalregion of the stent between an outer surface of the elongate releasemember distal region and an inner surface of the delivery shaft distalregion.
 5. The delivery device of claim 1, wherein the elongate releasemember distal region has a profile dimensioned to form a friction fitbetween the everted distal region of the stent and the delivery shaftdistal region.
 6. The delivery device of claim 5, wherein the deliveryshaft distal region includes a profile which complements the profile ofthe elongate release member distal region, and wherein the everteddistal region of the stent is frictionally held between the profile ofthe delivery shaft distal region and the profile of the elongate releasemember distal region.
 7. The delivery device of claim 6, wherein theelongate release member has sufficient strength in compression toadvance the elongate release member distal region distally in thedelivery shaft distal region to free the stent from the delivery shaftdistal region.
 8. The delivery device of claim 7, wherein a proximalregion of the elongate release member is externally accessible.
 9. Thedelivery device of claim 6, wherein the elongate release member hassufficient strength in tension to retract the elongate release memberdistal region proximally in the delivery shaft distal region to free thestent from the delivery shaft distal region.
 10. The delivery device ofclaim 9, wherein a proximal region of the elongate release member isexternally accessible.
 11. The delivery device of claim 1, wherein thelumen of the delivery shaft extends substantially from a proximal regionof the delivery shaft to the distal region of the delivery shaft. 12.The delivery device of claim 11, wherein the lumen of the delivery shaftincludes an intermediate region having an inside diameter dimensioned tosupport movement of the elongate release member.
 13. The delivery deviceof claim 1, further comprising a microcatheter having a proximal region,a distal region, and a lumen through at least the distal region of themicrocatheter, wherein the microcatheter distal region is disposed overthe delivery shaft distal region to support a proximal region of thestent in the lumen of the microcatheter adjacent the delivery shaft whenthe distal end of the elongate release member is disposed within thelumen of the delivery shaft.
 14. The delivery device of claim 1, whereindistal movement of the elongate release member disengages the elongaterelease member distal region from the the everted distal region of thestent and frees the stent from the delivery shaft.
 15. The deliverydevice of claim 1, wherein when releasably secured between the distalregion of the elongate release member and the distal region of thedelivery shaft, the entire everted distal region of the stent isdisposed within the lumen defined by the delivery shaft.